Background: Due to the coronavirus disease (COVID-19) pandemic, some authorities have implemented measures to control the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), such as quarantine. The aim of this systematic review was to summarize the results of the studies that investigated changes in eating habits, food intake, and body weight during the COVID-19 quarantine. Methods: This review followed the recommendations of the PRISMA protocol and has registration in the PROSPERO under number CRD42020212491. Searches used databases PubMed, Medline, Scielo, and Lilacs. Two authors conducted the selection process blindly and independently using the Rayyan software (QCRI). Of 5,248 papers, we included 28 studies. Results: Most of the included studies in this review presented data on changes in food intake (n = 22). These changes were especially towards the adoption of unhealthy eating habits such as an increase in the consumption of snacks and sweets; and a decrease in the intake of vegetables, fruits, fish, and dairy products (n = 21). Concerning body weight, the main change was towards weight gain (1.5 to 4.5 kg), which was positively associated with age (elderly); socioeconomic level (average socioeconomic level); increase of the intake of snacks, sweets, fried foods, and fast foods; and low consumption of vegetables. Besides, weight gain was inversely associated with physical activity and positively associated with sedentary time (n = 14).Conclusion: In this sense, the summarized evidence points to a change in eating habits, food intake, and body weight, as well as a relevant association between unhealthy eating choices and weight gain during quarantine. The COVID-19 quarantine caused an interruption in the routine of daily life, which generated an impact on mental health, 3 eating habits, and physical activity. This review showed that during the quarantine some individuals changed their eating habits, mainly towards the adoption of unhealthy habits and gained weight.